Merge-Delete Playlists will allow you to merge the track contents of two or more playlists to a new or existing playlist or delete any number of playlists at once, including Smart, Genius, and Playlist Folder playlists. The merge feature will prevent the same tracks that may appear in different source playlists from being duplicated and has an option to delete original playlists. The delete feature only deletes playlists; tracks, of course, remain in the library.
This latest version brings back Apple Music playlists detection; the last version removed this ability because I hadn't worked out all the details on how to handle them properly. They will appear with their names italicized at the top of the list in the window. It also fixes a bug that prevented selecting empty Playlist Folders.